Light emitting diodes known as LEDs have become very popular in the electrical/electronic industries. A light emitting diode is a solid state electronic component typically comprising a forward biased p-n semi-conductor junction diode. Light is emitted very close to, or within the junction region as injected holes and electrons diffuse across the junction and combine. The combining holes and electrons release energy and some of this energy is released directly as photons. Light emitting diodes can be fabricated by diffusing p and n type impurities into a suitable semi-conductor to form a junction. A semi-conductor commonly used to fabricate light emitting diodes which emit light in the visible spectrum, is gallium arsenide phosphide.
The diode is conventionally encapsulated in plastics and defines a cylindrical construction with a domed top, the diameter of the assembly being in the order of 5 mm.
Light emitting diodes perform a significant role in the electrical/electronic industry. They provide a simple and effective means of indicating a particular state of a variety of components in an electronic circuit. Their small size and durability makes them ideal for use on instrument panels and on circuit boards. They are frequently used to indicate the state of switching means and are often positioned adjacent to a switch to indicate the state of the switch.
In recent times companies such as Hewlett Packard have produced LEDs that incorporate integrated circuits within the structure of the LED.